Ambassador John Bolton Will Replace Gen. McMaster as National Security Adviser 3/23/2018 1:26:13 AM John Bolton, who will take office April 9, has met regularly with President Trump to discuss foreign policy Lt. Gen. McMaster is the latest in a series of high-profile exits from President Trump’s administration. He will be replaced as national security adviser by John R. Bolton, a former ambassador to the  United Nations  . WASHINGTON, The New York Times, March 22, 2018  — Lt. Gen. H. R. McMaster, the battle-tested Army officer tapped as President Trump’s national security adviser last year to stabilize a turbulent foreign policy operation, will resign and be replaced by John R. Bolton, a former United States ambassador to the United Nations, White House officials said Thursday. General McMaster will retire from the military, the officials said. He has been discussing his departure with President Trump for several weeks, they said, but decide...